var net = require('net'),
    http = require('http'),
    url = require('url'),
    fs = require('fs');
    
var DEFAULT_PORTS = {
    'http:': 80,
    'https:': 443
};

var INDEX_TPL = fs.readFileSync('index.html');

function _write(str, res, content_type){
    if (res.jsonp_cb) {
        str = res.jsonp_cb + '("' + str + '")';
    }
    res.writeHead(200, {
        'Content-Length': str.length,
        'Content-Type': content_type || 'text/plain'
    });
    res.end(str);
};

function expand(short_url, res){
    var info = url.parse(short_url);
    //  console.log('info: ' + JSON.stringify(info));
    if (info.protocol != 'http:') { // 无法请求https的url?
        _write(short_url, res);
        return;
    }
    var client = http.createClient(info.port ||
    DEFAULT_PORTS[info.protocol], info.hostname);
    var path = info.pathname || '/';
    if (info.search) {
        path += info.search;
    }
    var headers = {
        host: info.hostname,
        'User-Agent': 'NodejsSpider/1.0'
    };
    var request = client.request('GET', path, headers);
    request.end();
    request.on('response', function(response){
        if (response.statusCode == 302 ||
        response.statusCode == 301) {
            expand(response.headers.location, res);
        }
        else {
            _write(short_url, res);
        }
    });
};

//expand('http://sinaurl.cn/hbMUII');
// http服务
http.createServer(function(req, res){
    if (req.url.indexOf('/api?') == 0) {
        var params = url.parse(req.url, true);
        if (params.query && params.query.u) {
            if (params.query.cb) { // 支持jsonp跨域请求
                res.jsonp_cb = params.query.cb;
            }
            expand(params.query.u, res);
        }
        else {
            _write('', res);
        }
    }
    else {
        _write(INDEX_TPL, res, 'text/html');
    }
}).listen(1235);

process.on('uncaughtException', function(err){
    console.log('Caught exception: ' + err);
});

//	http://www.cnblogs.com/fengmk2/archive/2010/12/27/nodejs-urlexpand.html